Subwoofer speed is in the room, not the box
First, if you like swarm, that’s fine, please start a thread somewhere else about how much you like swarm.
I want to talk about the impression that subs are fast or slow compared to planar or line sources.
The concern, and it’s correct, is that adding a subwoofer to say a Martin Logan or Magneplanar speaker will ruin the sound balance. That concern is absolutely a valid one and can happen with almost any speaker, not just speakers with tight dispersion control.
What usually happens is that the room, sub and main speakers aren’t integrating very well. Unfortunately for most audiophiles, it’s very hard to figure out exactly what is wrong without measurements or EQ capabilities in the subwoofer to help you.
So, there’s the myth of a small sub being "faster." It isn’t. It’s slower has worst distortion and lower output than a larger sub but what it does is it doesn’t go down deep enough to wake the dragons.
The biggest problems I’ve heard/seen have been excessively large peaks in the subwoofer range. Sometimes those peaks put out 20x more power into a room than the rest of the subwoofer. Think about that!! Your 1000 W sub is putting out 20,000 watts worth of power in some very narrow bands. Of course that will sound bad and muddied. The combination of sub and main speaker can also excessively accentuate the area where they meet, not to mention nulls.
A lot is made about nulls in the bass but honestly IMHO, those are the least of our worries. Of course too many of them can make the bass drop out, but in practicality is is the irregular bass response and the massive peaks that most prevent any good sub from functioning well in a room.
Bass traps are of course very useful tools to help tame peaks and nulls. They can enable EQ in ways you can’t do without it. If your main speakers are ported, plug them. Us the AM Acoustics room mode simulator to help you place your speakers and listening location.
Lastly, using a subwoofer to only fill in 20 Hz range is nonsense. Go big or go home. Use a sub at least at 60 Hz or higher. Use a single cap to create a high pass filter. Use EQ on the subwoofer at least. Get bass traps. Measure, for heaven’s sake measure and stop imagining you know a thing about your speaker or subwoofer’s response in the room because you don’t. Once that speaker arrives in the room it’s a completely different animal than it was in the showroom or in the spec sheet.
Lastly, if your room is excessively reflective, you don’t need a sub, you need more absorption. By lowering the mid-hi energy levels in a room the bass will appear like an old Spanish galleon at low tide.
No. I want the sub to do the most it can do in the proper range to produce a fast, punchy sound (30 to 50hz). MORE gain not less. (BTW...16hz has no place in music.) Why would you do that? Just curious.
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Good topic. It’s nice to "get the low down" on subwoofers from guys with a lot of experience with the subject. Adding to the small vs large conversation: Its been stated that speaker distortion is directly proportional to the movement (excursion) of the cone. Double the excursion, double the distortion. Cut it in half ... half the distortion. Taking the popular 10" and 15" driver sizes as an example, the 15" has to move less than half as much as the 10 to produce the same volume of air. Assuming that things are somewhat linear here (the "motor" in the 15" has sufficient power to do what it does well), the 15" will be cleaner at a given frequency and sound level. So, what about the added "mass" of the 15? We have to keep in mind that some of the "added mass" is the weight of the air itself. At the same frequency and same volume level, the "weight" of the air being displaced will be exactly the same. The differences will be the moving mass of the additional cone material, larger voice coil, etc. on the 15" which will be minimized by the cone moving less than half as much as the 10". Cone breakup is another form of distortion on larger cones that may also be offset by less cone travel being introduced. The quality of the execution by the manufacturer will be a key element here, but it is entirely possible that larger woofers will, in fact, have less overall distortion and produce "tighter" base than a smaller woofer. We ordered in a 31" raw woofer many years ago because we were "hot rodders" who liked to mess with outrageous stuff. A 31" woofer has more cone area than 6 12" woofers, as a reference. I recalled mounting this thing in a 6 cubic foot sealed enclosure and running some test tones thru it. The rafters were, literally, shaking all over the building. A walk back to inspect the woofer revealed that the cone was moving about 1/4". There’s no substitute for cubic inches. |
@gdaddy1 wrote:
There are quite a few aspects to this. Depending on the nature of the bass response of both the main speakers and subs (from where they're positioned and further tweaked into place) there could be favorable scenarios for either solution, i.e.: a higher or lower subs-mains crossover point. Making a general statement however that subs can't reproduce the range up to ~100Hz without sounding boomy is simply incorrect. Main speakers are usually positioned as a compromise taking both the range above and below the Schroeder frequency into consideration, whereas subs can be dialed in for low frequency reproduction exclusively with rather elaborate corrective measures via positioning, added bass sources, DSP and other. Subs are also mostly actively configured, meaning direct amp-driver connection with dedicated amplification, much better woofer control to boot and a more efficient use of the power at one's disposal here without looking into a bunch of coils and what not of a passive filter. There's also the problematic aspect of crossing over in the middle of the central bass area - that is, in the 40-60Hz range - and mixing what is likely two different bass signatures here. You could argue any crossover point is a potential issue, but to my ears - again, depending on several factors - the less intervening and most advantageous crossover point to subs typically sits somewhere between 80-120Hz handing over to the upper bass area. This way the mains are effectively relieved of LF (not least important when the woofer/mids of the mains cover the entire power region up to ~450-ish Hz, and possibly even higher), and the subs cover the most energy-rich area to which they can be favorably dialed in and are better suited to tackle. Subs sounding "boomy" are most likely badly implemented and/or badly designed/constructed or simply too small. @tomic601 wrote:
Efficiency and low frequency reproduction means large size, and that again means the large cones/effective air radiation area generated move very little for a given SPL. Nothing "trashy" about that, but rather accommodated physics where they actually matter, but are less convenient for the interior decor-minded. Moreover, I can assure you "pistonic behavior" of well-designed typically pro segment woofers with anything but wobbly cones/suspensions here is the least of your worries in a domestic environment vs. a smaller and much less efficient driver (usually in the least efficient, sealed box with maximum cone movement at the tune) that needs excessive excursion by comparison for similar SPL. Potential mechanical noise issues galore, thermal compression creeping in, elevated distortion - you name it. +1 |
Ahem, well, that was addressed really early on, but this is conflating a number of issues. I specifically mentioned that peaks had to be dealt with, often by EQ or EQ + bass traps. Remove them and you can raise the subwoofer level, no problem. That’s a completely different issue than the crossover frequency. Same for using SWARM. I'd still recommend 80 Hz as an excellent starting point. Certainly better than 40 Hz. |
After many, many tests...I respectfully disagree. So does REL. From REL..."Almost 100% of the time, newcomers will set the crossover too high and the gain (volume level) too low. This will result in a sound that is fatter, boomier and improperly integrated with the main speakers. The secret is to realize the crossover needs to be lower than the main speaker’s output at which point the gain can be significantly higher resulting in very flat, natural and extended deep bass."
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